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PowerShell Desired State Configuration has been a favorite among Windows infrastructure engineers for years, and the advent of the VMware DSC module means users who already use DSC to manage Windows servers can use it to manage VMware, too. As VMware has continued to develop the module, it has increased the numbers of vSphere components the tool can manage, including VMware Update Manager.
DSC has been the configuration management tool of choice for Windows since it was released. No other tool offers such a wide array of capabilities to manage a Windows OS in code instead of through a GUI.
VMware also uses PowerShell technology to manage vSphere. The vendor officially states that PowerCLI, its PowerShell module, is the best automation tool it offers. So, it only makes sense that VMware would eventually incorporate DSC so that its existing PowerShell customers can manage their assets in code.
Why use DSC?
Managing a machine through configuration as code is not new, especially in the world of DevOps. You can write a server's desired state in code, which ensures you can quickly resolve any drift in configuration by applying that configuration frequently.
In vSphere, ESXi hosts, in particular, are the prime candidates for this type of management. An ESXi host's configurations do not change often, and when they do happen to change, admins must personally make that change. This means any change in the DSC configuration will apply to the hosts.
You can use this tool to manage a number of vSphere components, such as VMware Update Manger and vSphere Standard Switch.
How the LCM works
In DSC, Local Configuration Manager (LCM) makes up the brains of a node. It takes in the configuration file and then parses and applies the change locally.
ESXi and vCenter do not have LCM, so in the context of vSphere, you must use an LCM proxy, which runs as a Windows machine with PowerShell v5.1 and PowerCLI 10.1.1.
Installing the module
Installing the module is simple, as the DSC module is part of PowerShell Gallery. It only takes a single cmdlet to install the module on your LCM proxy:
C:\> Install-Module -Name VMware.vSphereDSC
Updating the module when Windows releases additional versions is also a simple task. You can use the Update-Module cmdlet in PowerCLI:
C:\> Update-Module vmware.vspheredsc
DSC ties a resource to a particular area of a system it can manage. The DSC module vmware.vspheredsc, for example, can manage various aspects of vSphere, such as the following:
C:\Users\dan> Get-DscResource -Module vmware.vspheredsc | Select Name
Many such resources are associated with ESXi hosts. You can manage settings such as accounts, Network Time Protocol and service through DSC. For clusters, manage settings such as HAEnabled, Distributed Resource Scheduler and DRS distribution. You can view the resources DSC can manage with the Get-DSCResource cmdlet:
C:\> Get-DscResource -Name Cluster -Module vmware.vspheredsc -Syntax
Cluster [String] #ResourceName
[DependsOn = [String]]
[PsDscRunAsCredential = [PSCredential]]
Server = [String]
Credential = [PSCredential]
Name = [String]
Location = [String] DatacenterName = [String]
DatacenterLocation = [String]
Ensure = [String]
[HAEnabled = [Boolean]]
[HAAdmissionControlEnabled = [Boolean]]
[HAFailoverLevel = [Int32]]
[HAIsolationResponse = [String]]
[HARestartPriority = [String]]
[DrsEnabled = [Boolean]]
[DrsAutomationLevel = [String]]
[DrsMigrationThreshold = [Int32]]
[DrsDistribution = [Int32]]
[MemoryLoadBalancing = [Int32]]
[CPUOverCommitment = [Int32]]
With the capabilities of DSC now available to VMware admins, as well as Windows admins, they can control a variety of server variables through code and make vSphere and vCenter automation easy and accessible. They can apply broad changes across an entire infrastructure of hosts and ensure consistent configuration.